In this 2014 animated sequel, Hiccup and Toothless discover a secret ice cave that is home to hundreds of new wild dragons and the mysterious Dragon Rider, who turns out to be Hiccup's long-lost mother, Valka. What is the title of this film?

The film described, where Hiccup and Toothless discover a secret ice cave home to new dragons and Hiccup's long-lost mother, Valka, is indeed How to Train Your Dragon 2 (Review). This animated sequel, released in 2014, continues the adventures of the Viking teenager Hiccup and his loyal dragon, Toothless, five years after the events of the first film. Their journey of exploration leads them to uncover a hidden dragon sanctuary and a pivotal character from Hiccup's past.

The discovery of Valka, voiced by Cate Blanchett, is a central emotional arc of the film. She is revealed to be a formidable Dragon Rider who has spent two decades rescuing dragons and bringing them to this secret haven, believing them to be safer away from human conflict. Her reunion with Hiccup and his father, Stoick the Vast, adds significant depth to the story, exploring themes of family, loss, and understanding. The film expands the world of dragons and Vikings (Review), introducing new species and a powerful villain, Drago Bludvist, who threatens the peaceful coexistence Hiccup has worked to establish.

"How to Train Your Dragon 2" was widely praised by critics for its stunning animation, emotional depth, and engaging storyline. It built upon the success of its predecessor, deepening the characters and expanding the mythology of the dragon world. The film's director, Dean DeBlois, envisioned the "How to Train Your Dragon" series as a trilogy, aiming to tell a larger, interconnected story rather than just standalone adventures, and this sequel played a crucial role in that grand narrative. Its critical acclaim and box office success solidified its place as a beloved installment in the animated film landscape.